This invention relates generally to semiconductor wafer processing and more particularly to the optimization of wafer sawing using an internal diameter saw blade.
In semiconductor wafer preparation the flatness, depth of damage and edge perfection of a wafer are dependent upon the degree to which the internal diameter saw blade follows an ideal plane as it traverses the wafer, and its freedom from out-of-plane vibration. To meet these requirements the saw blade must be kept under a constant, high tension. An improperly tensioned blade will produce bowed or otherwise defective wafers and the useful life of the blade will be diminished, because the blade becomes unstable with respect to deviation under the forces of cutting. Further, the blade becomes free to vibrate with a greater amplitude than a properly tensioned blade.
Methods and apparatus are known in the art for monitoring blade deviation or displacement from a steady-state position as it moves through a crystal. However, these systems do not indicate whether the blade requires retensioning or merely needs dressing. If the blade is dressed when retensioning was the proper course of action, the result will be lower wafer quality and yield.
It is known in the art to measure blade tension by applying a force to the blade rim through a force gauge or a balance arm in contact with the blade and then reading deflection with a dial indicator. This method, however, requires stopping the saw, assembly and calibration of sensitive, precision equipment, and numerous measurements by a skilled operator. This is both expensive and time consuming.